In mining, ore beneficiation, and certain industrial processes, there often are produced highly acidic slurries containing inorganic gels and dispersed, particulate incompressible solids. Ordinarily, dispersed solids can be recovered by filtration, or settling which is often aided by flocculating agents. However, the presence of gels clog filters and greatly slow settling rates, and thus render such removal means ineffective. Also, many polymeric flocculants appear not to function well in this media because they are degraded by the highly acidic conditions and produce a poor quality floc.
A good example of the foregoing problem is in the chloride process for producing titanium dioxide pigment. In such process, titanium containing ore or material is chlorinated in a fluidized bed reactor in the presence of coke or other carbonaceous material. Metal chlorides and fine, particulate coke and ore are entrained in the hot gases exiting the chlorinator. Subsequently, the titanium tetrachloride is separated from the other materials and is processed into titanium dioxide pigment. The byproduct stream containing various metal chlorides and coke and ore is then quenched in water.
In such chloride process, it would be desirable to be able to separate the coke and ore from the soluble metal chlorides. However, because the slurry is highly acidic and contains inorganic gels formed from certain of the metal chlorides, the foregoing removal problems are present. Thus, a process is needed to recover the valuable components from this byproduct stream.
The following information is provided which may be of interest to this invention:
U.S. Pat. No. 3,959,465 discloses a process for concentrating titanium minerals by leaching with an acid in the presence of a polyacrylamide surfactant, whereby formation of very fine particles of the titanium mineral is inhibited, while iron is removed.
U.S. Pat. No. 4,698,171 describes agents for selective flocculation of fine aqueous suspensions of titanium and iron ores comprising polymers containing olefinic monomer units based on 3,4-methylenedioxy- or 3,4-di:hydroxybenzene derivatives.
Russian patent SU-1204568 discloses a process for rapid clarification of sulfuric acid ilmenite slurries by flocculating with an aminomethylated copolymer of acrylamide with ethanolamine acrylate or the Na salt of maleic anhydride.
Russian patent SU-865837 discloses a process for purifying aqueous effluent from the sulfate process for making TiO.sub.2. The effluent containing H TiO.sub.2, and metal salts is neutralized and freed from metal ions by a combined operation of flocculation with polyacrylamide and flotation of the solid phase with alkyl-benzyldi:methyl-ammonium chloride surfactant.
Belgian patent BE 848271 discloses a process for clearing acid titanium sulfate liquor obtained in the sulfate process for making TiO.sub.2, using water soluble methylolated acrylamide polymers as flocculating agent.
Japanese patent 6,031,058 discloses the manufacture of iron oxide with reduced silicon content. The process includes using a high molecular weight cationic polyacrylamide flocculant.
Japanese Published Patent Application 123,511 (published 9/29/75) discloses a process for purifying TiO.sub.2 ores by leaching with a chelating agent, surfactant, and polyacrylamide coagulant.